Analytical performances of a flow electrochemical sensor for preconcentration and stripping voltammetry of metal ions

Continuous flow analytical systems are advantageous because they are easily automatable and allow to approach the ideal real-time analysis. A flow electroanalytical system for trace analysis, using a graphite felt as working electrode is reported here. The detection is performed in two steps: the preconcentration of the analyte by complexation with coordinating sites present on the electrode and the analysis by linear sweep stripping voltammetry. Carboxylate groups naturally present on graphite felt were used in this first study as receptors for the preconcentration step. The factors affecting the performances of the flow sensor are reported. The flow system presents several advantage compared with a static one: an increase of the kinetic of complexation during the preconcentration of the analyte on the electrode and a good control of the volume of the analyzed solution in contact with the electrode. A calibration curve typical of an equilibrium process was obtained for lead ions with a limit of detection of 10−9 mol L−1, showing the ability of unmodified graphite felt to complex Pb2+.